Apparatus for purifying in continuous casting silicon- and/or aluminium-killed steel

ABSTRACT

An apparatus for purifying silicon- and/or aluminium-killed steel in a continuous casting process utilizing a tundish disposed between the casting ladle and the continuous casting machine. a tube extends from the casting ladle into the tundish and terminates shortly above the bottom of the latter. A trough on the bottom of the tundish forms conjointly with the tube a guide for the steel directing same into soft contact with the purifying slag upon the steel bath.

United States Patent [1 1 [111 3,887,171 Neuhaus June 3, 1975 [S4] APPARATUS FOR PURIFYING IN 3,343,828 9/1967 Hunt 266/34 V 3,514,519 5 1970 Schempp et a1. 164/281 X AND/0R 3,780,788 12/1973 Sundy 164/281 X 3,814,167 6/1974 Listhuber et a1 164/82 Inventor: Herbert Neuhaus, Duisburg,

Germany Kliiekner-Werke AG, Duisburg, Germany Filed: Nov. 28, 1973 Appl. No.: 419,708

Assignee:

Foreign Application Priority Data Mar. 12, 1973 Germany 2312137 Primary ExaminerGera1d A. Dost Attorney, Agent, or FirmRoss, Ross & Flavin [57] ABSTRACT An apparatus for purifying siliconand/or aluminiumkilled steel in a continuous casting process utilizing a tundish disposed between the casting ladle and the continuous casting machine. a tube extends from the casting ladle into the tundish and terminates shortly above the bottom of the latter. A trough on the bottom of the tundish forms conjoint1y with the tube a guide for the steel directing same into soft contact with the purifying slag upon the steel bath.

4 Claims, 2 Drawing Figures ll l APPARATUS FOR PURIFYING IN CONTINUOUS CASTING SlLlCON- AND/OR ALUMINIUM-KILLED STEEL The present invention relates to an apparatus for purifying in continuous casting siliconand/or aluminiumkilled steel, utilizing a tundish, which apparatus is arranged between the casting ladle and the continuous casting machine, wherein a tube is provided. which tube extends from the casting ladle into the tundish and terminates shortly above the bottom of the latter.

During continuous casting of siliconand/or aluminium-killed steel, inclusions consisting of silicates or alumina occur in the quenching zone of the preliminary slabs or steel billets. The latter have to be removed by scarfing or grinding, whereby losses of between 4% and 5% are considered tolerable These inclusions are caused by deoxidation products which have not separated off during deoxidation with silicon and/or aluminium and also, however secondary, by inclusions which are produced during the casting process as a result of the steel coming into contact with the air. Conditions can be considerably improved by casting through a casting tube arranged under the casting ladle. This casting process, however, is not satisfactory for a high quality preliminary slab which allows no scarfing losses.

An apparatus is known providing a refractory tube inside the tundish, which extends nearly from the cover of the tundish into the trough arranged thereunder. Thus the tube and the trough effect the guidance of the steel. In the inner part of the tube, there is a slag which has a purifying effect on the steel, flowing through the slag during continuous casting.

During the casting of the steel out of the casting ladle into the tindish, the steel stream travels through a pass of more than one meter between the casting ladle and tundish, coming into direct contact with the air; thus further oxidation impurities may occur. These impurities, too, must be removed. Thus it is more favourable to prevent, during casting, the formation of further impurities on account of the oxidation by air so that the steel has a lower content of inclusions.

The object of the invention is to provide an apparatus which does not suffer from the disadvantages mentioned above but which is constructed in such a way that a better purification of steel can be effected than has been possible up to now.

According to the invention, there is provided a trough on the bottom of the tundish and a tube effecting conjointly with said trough a guidance on the steel, which is to be softly contacted by the slag which covers the bath of steel and which has a purifying effect.

It is advisable to utilize a slag, having a composition which absorbs in particular alumina or silicates.

During the casting of the steel, the latter flows first out of the casting ladle through the tube into the trough and there, by reason of the guidance between tube and trough, the steel comes into soft contact with the purifying slag covering the steel; thus a good purification can be effected.

According to another feature of the invention, the outside diameter of the tube and the inside diameter of the trough are so dimensioned that the free flowsection between them is so much narrower that a higher flow-velocity is achieved in said section than the flow-velocity existing in one or more immersion tubes connected with the tundish.

Furthermore, it is advisable that the trough in the tundish extend into the slag, covering the steelbath in the tundish.

It is also possible to provide, instead of the trough, a refractory ring, constructed like the trough, for the guidance of the steel.

According to a further feature of the invention, a set of barriers is provided on the bottom of the tundish. By reason of the resulting turbulent streams, it may be possible to absorb slag particles or other impurities contained in the steel.

It is furthermore advisable to provide immersion tubes in the tundish through which the impurified steel can flow into the continuous casting mould.

FIG. 1 shows a longitudinal section through the tundish and FIG. 2 shows a section along the line ll-ll of FIG. 1.

By means of the apparatus shown in the drawing, it is possible to purify siliconand/or aluminiumkilled steel during continuous casting. The tundish 2, having a trough 4 in its bottom 3, is arranged between the casting ladle l and the continuous casting machine, both not being shown in detail. The tube 6 extends through the cover 5 of the tundish 2 into the interior of the tundish in such a way that the tube 6 forms a guidance together with the trough 4. A set of barriers 7 is arranged on the bottom 3 of the tundish 2. The tundish 2 has one or two immersion nozzles 8 through which the steel flows into the moulds, not shown in detail.

During continuous casting of the steel, the latter flows following the direction of the arrow 9 out of the casting ladle 1 through the tube 6 into the trough 4 of the tundish 2. Now the steel rises and flows in direction of arrow 10, thereby crossing the wall of the trough 4, the steel thus coming into firm contact with the slag 12 which has a purifying effect and which covers the steel 11. By reason of the barriers 7, a turbulence occurs, thereby driving most of the impurities into the slag 12.

What we claim is:

1. Apparatus for purifying molten siliconand/or aluminium-killed steel with the aid of a purifying slag upon the molten metal in a continuous casting process and disposed between the casting ladle and a continuous casting machine comprising:

a tundish, 1

a tube extending from the casting ladle into the tundish and terminating just above the bottom of the tundish,

a trough in the bottom of the tundish,

a guidance for the molten metal defined by the tube and trough for directing the molten metal upwardly in soft touching contact with the purifying slag.

2. ln an apparatus as claimed in claim 1, wherein the outside diameter of the tube and the inside diameter of the trough being dimensioned with the free flowsection between them being much narrower for the attainment of a higher flow-velocity through the section than the flow-velocity existing in one or more immersion tubes connecting the tundish with the nozzles.

3. In an apparatus as claimed in claim 1, wherein a set of barriers is provided on the bottom of the tundish.

4. In an apparatus as claimed in claim 1 wherein immersion tubes are provided in the tundish. 

1. APPARATUS FOR PURIFYING MOLTEN SILICON- AND/OR ALUMINIUM-KILLED STEEL WITH THE AID OF A PURIFYING SLAG UPON THE MOLTEN METAL IN CONTINUOUS CASTING MACHINE COMPRISTHE CASTING LADLY AND A CONTINUOUS CASTING MACHINE COMPRISING A TUNDISH, A TUBE EXTENDING FROM THE CASTING LADLE INTO THE TUNDISH AND TERMINATING JUST ABOVE THE BOTTOM OF THE TUNDISH, A TROUGH IN THE BOTTOM OF THE TUNDISH, A GUIDANCE FOR THE MOLTEN METAL DEFINED BY THE TUBE AND TROUGH FOR DIRECTING THE MOLTEN METAL UPWARDLY IN SOFT TOUCHING CONTACT WITH THE PURIFYING SLAG.
 1. Apparatus for purifying molten silicon- and/or aluminium-killed steel with the aid of a purifying slag upon the molten metal in a continuous casting process and disposed between the casting ladle and a continuous casting machine comprising: a tundish, a tube extending from the casting ladle into the tundish and terminating just above the bottom of the tundish, a trough in the bottom of the tundish, a guidance for the molten metal defined by the tube and trough for directing the molten metal upwardly in soft touching contact with the purifying slag.
 2. In an apparatus as claimed in claim 1, wherein the outside diameter of the tube and the inside diameter of the trough being dimensioned with the free flow-section between them being much narrower for the attainment of a higher flow-velocity through the section than the flow-velocity existing in one or more immersion tubes connecting the tundish with the nozzles.
 3. In an apparatus as claimed in claim 1, wherein a set of barriers is provided on the bottom of the tundish. 